The present invention relates to a method for preventing gelation in waste wash water which contain glues or varnishes of resorcinol resins or phenol modified resorcinol resins.
Resorcinol resins made by reacting resorcinol with formaldehyde, or phenol modified resorcinol resins made by reacting resorcinol and phenol with formaldehyde have the advantage of curing at ambient or lower temperatures by adding formaldehyde donors. Therefore, they have a wide range of practical uses when used as adhesives or varnishes.
However, this advantage which makes the cure proceed at ambient temperature when applied as adhesives or varnishes reacts adversely, on the other hand, to the wastes resulting from washing the mixers, spreaders and other tools and machines used with such adhesives, thereby transforming them into a watery, gelatinous, agar-agar state within a several day period, during which the curing reaction between resorcinol resin or phenol modified resorcinol resin and the formaldehyde donor proceeds gradually at ambient temperature. Resorcinol resins or phenol modified resorcinol resins are usually made into glues or varnishes by adding paraformaldehyde or formalin as a hardener immediately before use. Waste water from washing the equipment and machines used for mixing and applying those glues or varnishes are deep reddish brown and show a high chemical oxygen demand (COD) and biochemical oxygen demand (BOD), because the waste water contains free resorcinol, free phenol, free formaldehyde, etc. besides resinous matters. Therefore, it is necessary to make such washing wastes harmless by chemical or chemical engineering treatments, or to incinerate them. It is usual to store the waste wash water after collecting up to some large volume, at which time the forming of a watery agar-agar state gel during storage of such washing wastes at ambient temperature as described above becomes an issue. Namely, chemical treatments such as oxidizing or an aggregation-separating and the like of the waste wash water are applicable only when the wastes are in very low viscosity liquid state. On the other hand, the gel state of those washings are difficult to burn, so if it is burnt, such washings must be kept in liquid state and burned in an incinerator with the use of a heavy or light oil burner as accelerator.